Texture greyed out in render
The greyed parts of texture are the parts with high reflection, so they reflect black background and this cause this effect. 

Glossy shader is connected to bottom input, so value 1 in Fac slot make material pure glossy, value 0 is pure diffuse. This values are stored in texture as a colors: 1 = white, 0 = black.

What do you need to do is change white to grey, so from value 1 to smaller one.

One way how to do it is plug ColorRamp node between texture and Fac slot on  Mix Shader Node. 
Now you can control values by colors. In this case you need to change white to appropriate gray = change value from 1 to less than one.

Also you can moving slides closer together and adjust contrast.

As second - for nice reflections you need something to reflect. Usually hdri environment map. You have black environment in your scene = black color in reflected from your materials = ugly grayed reflections.